<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - WebXR - Look to Select w/cursor</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import {VRButton} from 'three/addons/webxr/VRButton.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});
  renderer.xr.enabled = true;
  document.body.appendChild(VRButton.createButton(renderer));

  const fov = 75;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 50;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.set(0, 1.6, 0);

  const scene = new THREE.Scene();
  {
    const loader = new THREE.CubeTextureLoader();
    const texture = loader.load([
      'resources/images/grid-1024.png',
      'resources/images/grid-1024.png',
      'resources/images/grid-1024.png',
      'resources/images/grid-1024.png',
      'resources/images/grid-1024.png',
      'resources/images/grid-1024.png',
    ]);
    scene.background = texture;
  }

  {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(-1, 2, 4);
    scene.add(light);
  }

  function makeDataTexture(data, width, height) {
    const texture = new THREE.DataTexture(data, width, height, THREE.RGBAFormat);
    texture.minFilter = THREE.NearestFilter;
    texture.magFilter = THREE.NearestFilter;
    texture.needsUpdate = true;
    return texture;
  }

  const boxWidth = 1;
  const boxHeight = 1;
  const boxDepth = 1;
  const boxGeometry = new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth);

  const sphereRadius = 0.5;
  const sphereGeometry = new THREE.SphereGeometry(sphereRadius);

  function makeInstance(geometry, color, x) {
    const material = new THREE.MeshPhongMaterial({color});

    const cube = new THREE.Mesh(geometry, material);
    scene.add(cube);

    cube.position.x = x;
    cube.position.y = 1.6;
    cube.position.z = -2;

    return cube;
  }

  const meshToMeshMap = new Map();
  [
    { x:  0, boxColor: 0x44aa88, sphereColor: 0xFF4444, },
    { x:  2, boxColor: 0x8844aa, sphereColor: 0x44FF44, },
    { x: -2, boxColor: 0xaa8844, sphereColor: 0x4444FF, },
  ].forEach((info) => {
    const {x, boxColor, sphereColor} = info;
    const sphere = makeInstance(sphereGeometry, sphereColor, x);
    const box = makeInstance(boxGeometry, boxColor, x);
    // hide the sphere
    sphere.visible = false;
    // map the sphere to the box
    meshToMeshMap.set(box, sphere);
    // map the box to the sphere
    meshToMeshMap.set(sphere, box);
  });

  class PickHelper {
    constructor(camera) {
      this.raycaster = new THREE.Raycaster();
      this.pickedObject = null;
      this.pickedObjectSavedColor = 0;

      const cursorColors = new Uint8Array([
        64, 64, 64, 64,       // dark gray
        255, 255, 255, 255,   // white
      ]);
      this.cursorTexture = makeDataTexture(cursorColors, 2, 1);

      const ringRadius = 0.4;
      const tubeRadius = 0.1;
      const tubeSegments = 4;
      const ringSegments = 64;
      const cursorGeometry = new THREE.TorusGeometry(
          ringRadius, tubeRadius, tubeSegments, ringSegments);

      const cursorMaterial = new THREE.MeshBasicMaterial({
        color: 'white',
        map: this.cursorTexture,
        transparent: true,
        blending: THREE.CustomBlending,
        blendSrc: THREE.OneMinusDstColorFactor,
        blendDst: THREE.OneMinusSrcColorFactor,
      });
      const cursor = new THREE.Mesh(cursorGeometry, cursorMaterial);
      camera.add(cursor);
      cursor.position.z = -1;
      const scale = 0.05;
      cursor.scale.set(scale, scale, scale);
      this.cursor = cursor;

      this.selectTimer = 0;
      this.selectDuration = 2;
      this.lastTime = 0;
    }
    pick(normalizedPosition, scene, camera, time) {
      const elapsedTime = time - this.lastTime;
      this.lastTime = time;

      const lastPickedObject = this.pickedObject;
      // restore the color if there is a picked object
      if (this.pickedObject) {
        this.pickedObject = undefined;
      }

      // cast a ray through the frustum
      this.raycaster.setFromCamera(normalizedPosition, camera);
      // get the list of objects the ray intersected
      const intersectedObjects = this.raycaster.intersectObjects(scene.children);
      if (intersectedObjects.length) {
        // pick the first object. It's the closest one
        this.pickedObject = intersectedObjects[0].object;
      }

      // show or hide cursor
      this.cursor.visible = this.pickedObject ? true : false;

      let selected = false;

      // if we're looking at the same object as before
      // increment time select timer
      if (this.pickedObject && lastPickedObject === this.pickedObject) {
        this.selectTimer += elapsedTime;
        if (this.selectTimer >= this.selectDuration) {
          this.selectTimer = 0;
          selected = true;
        }
      } else {
        this.selectTimer = 0;
      }

      // set cursor material to show the timer state
      const fromStart = 0;
      const fromEnd = this.selectDuration;
      const toStart = -0.5;
      const toEnd = 0.5;
      this.cursorTexture.offset.x = THREE.MathUtils.mapLinear(
          this.selectTimer,
          fromStart, fromEnd,
          toStart, toEnd);

      return selected ? this.pickedObject : undefined;
    }
  }

  const pickHelper = new PickHelper(camera);
  scene.add(camera);

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  function render(time) {
    time *= 0.001;

    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }

    let ndx = 0;
    for (const mesh of meshToMeshMap.keys()) {
      const speed = 1 + ndx * .1;
      const rot = time * speed;
      mesh.rotation.x = rot;
      mesh.rotation.y = rot;
      ++ndx;
    }

    // 0, 0 is the center of the view in normalized coordinates.
    const selectedObject = pickHelper.pick({x: 0, y: 0}, scene, camera, time);
    if (selectedObject) {
      selectedObject.visible = false;
      const partnerObject = meshToMeshMap.get(selectedObject);
      partnerObject.visible = true;
    }

    renderer.render(scene, camera);
  }

  renderer.setAnimationLoop(render);
}

main();
</script>
</html>

